Thomas a



(No Model.)

A. EDISON.

CARBON FOR ELECTRIC LAMPS. No. 251,540. Patented Dec. 27,1881.

. $4 .1. ,1 1:.- I Q 4 s WITNESSES: INVENTOR:'

ATTORNEYS.

N. FEIERS. Plmwmho ra lm. Wildlininn, D. C.

UNITED STATES PATENT OFFICE.

THOMAS A. EDISON, OF MENLO PARK, NEW JERSEY, ASSIGNOR TO THE EDISON ELECTRIC LIGHT COMPANY, OF NET V YORK, N. Y.

CARBON FOR ELECTRIC LAMPS.

SPECIFICATION forming part of Letters Patent No. 251,540, dated December 2'7, 1881. Application filed August 6, 1880. (No model.)

To all whom it may concern:

Be it known that I, THOMAS A. EDISON, of Menlo Park, in the county of Middlesex and State of New Jersey, have invented a new and useful Improvement in Garbons for Electric Lamps; and I do hereby declare that the following is a full and exact description of the same, reference being had to the accompanying drawings, and to the letters of reference marked thereon.

In incandescent electric lighting I prefer to use for the incandescing conductorasmall slip or filament of carbon bent into a curve, now generally designated the horseshoe carbon. Great success has attended the use of such carbons made from a naturally fibrous material capable of carbonization-for instance, wood formed into proper shape and then carbonized. I have found, however, that thebest results are attained with the use of those materials which are fibrous, and wherei n the fibers making up the mass of material lie naturally parallel, so that the individual fibers extend from end to end, increasing its strength and obviating danger of breakage from cross or 0blique grain.

To produce the best results in giving light it is essential that the carbons should be of uniform size throughout the portion that is rendered incandescent, in order that radiatingsurface and resistance be regularand uniform, insuring even heating and incandescence.

The object of this invention, therefore, is to produce-asmall slip or filament for the carbon having parallel fibers and of uniform size; and to this end it consists in a carbon made of the materials and in the way more particularly hereinafter described and claimed.

I have found that for the purposes of the carbon filamenteane bamboois eminentlysuited, it having long parallel fibers, and with a minimum of cementingor other foreign matters. The cane bamboo is cntinto strips, from which the hard glossyor silicious exterior and the pithy interior have been before removed, or from which they are now removed. Each strip is then out or shaved by proper devices or machinery until its body, or part intended for ligl1t-giving,is reduced to the desired form and size, the ends being formed into enlargements, afiording a good bearing or surface for uniting the finished carbons to metallic conductors. It is preferable that these enlarge ments of the ends be formed entirely upon side of the finished slip which forms the blank for carbonization, instead ofupon both sides. This construction enables the blank, when placed on edge in the carbonizer, to more readily move therein as itis contracted in the process ofcarbonization. As the material shrinks in the process of carbonization, the finished carbon being smaller than the blank, allowance is to be made therefor in preparing the blanks, and they should be made proportionately larger than the size desired for the finished carbon. One or a number of blanks thus prepared are then placed in a suitable carbonizing oven or flask and thoroughly carbonized.

In the drawings, Figure 1 represents a blank made from cane bamboo, ready for carbonization, having enlarged or clamping ends 8 3 formed on one edge only, while in these enlarged or clamping ends are theslots 0' i, by which the slips may be secured in the carbonizer, and which also mayform the holes through which pass the screws or clamps, ifclamps be used for securing the finished carbon to leading-in wires. Fig. 2 shows in perspective a finished carbon made from the blankshown in Fig.

What I claim is- 1. A slip or filament'for forming on carbonization the inoandescing conductor of an electric light, made ofbamboo or similar fiber, substantially as set forth.

2. An incandescing carbon conductor for electric lights, made from cane bamboo or sim ilar fiber, substantially as set forth.

This specification signed and witnessed this 28th day of July, 1880.

THOS. A. EDISON. Witnesses:

CHAS. BATCHELOR, G. E. GOURAND. 

